How can I avoid this camera tracking error? "Some data failed to reconstruct (see console for details)"
Simple:
Here are a few measures to fix this issue:
Take good footage that isn't to shaky or blurred.
Double check that all of your tracks are accurate.
Add more accurate tracks.
Delete a track, then solve camera motion if it didn't help, chose a different track and then and repeat.
make sure that not all your tracks are on one single plane in space (eg. on a wall)
If all fails, then your shot is simply to difficult to solve.